Adjustable jet nozzle for aircraft propulsion



Feb. 12, 1952 R, P'LATH 2,585,270

ADJUSTABLE JET NOZZLE FOR AIRCRAFT PROPULSION Filed March 12, 1945INVENTOR. ROBE/PT PLA TH BY A TTORNEKS Patented Feb. 12, 1952 ADJUSTABLEJET NOZZLE FOR AIRCRAFT PROPULSION Robert Plath, Seattle, Wash.,assignor to Boeing Airplane Company, a corporation of DelawareApplication March 12, 1945, Serial No. 582,257

9 Claims.

My invention relates to a reactive jet structure capable of adjustmentto vary the effective size of the jet orifice for regulating the actionof the jet. The improvement is particularly applicable to jet motors foraircraft propulsion purposes.

Sometimes it is desirable to alter the eifective area of the orificethrough which the jet of a jet motor is projected, but any mechanismintended for such adjustment should be rugged and reliable.

It is the principal object of my invention to provide jet orificeadjusting mechanism which is simple, effective, and easy tooperate, anda further object is to shield such mechanism from direct exposure to theintense heat of the gases projected through the orifice.

Another object of my invention is to enable the size of the jet orificeto be varied within wide limits by comparatively little movement of theadjusting mechanism. My structure may be designed, however, to require agreater or lesser movement of the adjusting mechanism in order to obtaina given variation in size of orifice.

Two representative forms of my adjustable orifice nozzle are shown inthe accompanying drawing, and additional advantages of these particularembodiments will be discussed hereafter.

Figure 1 is a side elevation view of one type of adjustable orifice jetnozzle incorporating my invention, and Figure 2 is an' end elevationalview thereof.

Figure 3 is a view similar to Figure 1 showing the parts in differentadjusted positions, and Figure 4 is an end elevational view of thenozzle with the parts in such different positions.

Figure 5 is an end elevational view of a different form of adjustableorifice jet nozzle, and Figure 6 is a longitudinal sectional view of thesame nozzle taken on line 6-43 of Figure 5.

Conventional reaction jet nozzles used for propulsion purposes include atubular portion I, which may be cylindrical and terminate in aconstricted tip ll] of rearwardly tapering frustoconical shape. The bodyI and tip 10, however, invariably are integrated into a singlecontinuous tube. In the present structure the main tube I and its tipare preferably circular in cross section, although they may be of othershape, and likewise are integrated in the forms shown in Figures 1 to 4,inclusive, to the extent that they constitute a single integralstructure when the nozzle has been completed. Thus the tip is secured tothe tube I and supported from it. by connecting bars Il, spacedcircummmntiany I 2 about the tube and extending lengthwise of it. Thesebars may be welded or otherwise rigidly and permanently attached to eachnozzle part.

The wall of the nozzle tube is not continuous despite its integralconstruction, the rear edge l2 of the cylindrical tube section I and theforward edge [3 of the frusto-conical tubular tip 10 being arranged inaxially spaced relationship to define an annular aperture between thetube parts. Such aperture between the nozzle tube parts is not leftunrestricted in a radial direction, however, but can be closedcompletely by an encircling tube or sleeve arranged telescopically andconcentrically relative to the inner tube. Such sleeveis similar to theinner tube in cross-sectional shape and includes a cylindrical section14, fitting snugly over the cylindrical portion l of the nozzle tube,and a rearwardly tapered frustoconical tubular portion 15 having a coneangle equal to the cone angle of tip Hi. The length of thefrusto-conical portion of the outer tube is sufiiciently great tobridge'between the rear edge l2 of the cylindrical nozzle portion andthe forward end iii of the tip portion.

Although the encircling sleeve I4, l5 fits snugly over nozzle tube I itis slidable axially relative to it to vary the opening between the tubeproper andtip It. In the position of the sleeve closing the nozzleaperture the rearward end of the outer .tube l5 will engage contiguouslythe forward portion of the outer surface of the inner tip tube It, sothat the wall of the composite jet nozzle will be continuous from tube Ito the rearward end of tip 10. With the adjustable tube in such closedposition the nozzle functions in the conventional manner. 1

As the outer tube 14, l 5 is slid lengthwise rearwardly relative to tubel and tip I 0 from the position shown in Figures 1 and 2 into a positionsuch as shown in Figures 3 and 4, the annular aperture between thenozzle tube and its tip is between the rearward end of sleeve l4 and theadjacent portion of the inner tube.

Because of the larger. area through which the gases can escape'theirvelocity will be less than when the sleeve. is in the fully closedposition of Figure 1. Moreover, the farther sleeve I4 is slid rearwardlythe greater will be the radial width of the annular opening between thetelescoping tubes, and consequently the larger will be the aggregatenozzle discharge area. The jet orifice will reach its maximum size,equal to the area of the rearward end of outer tube l4, l5, when suchrearward end has been moved rearward far enough to lie in the same planetransversely of the nozzle tubes as the rearward end of the inner tubeHi.

When the nozzle area adjustment is effected by an external slidingsleeve, such as the tube l4, IS, the cylindrical portion in engagementwith tube l is not exposed directly to the jet gases, and consequentlysuch portion will remain comparative- 1y cool. Moreover the nozzle inthat event is not obstructed by mechanism required to control thesliding of the orifice adjusting tube. The particular type of adjustingmechanism employed is not of great importance, a rod is pivotallyconnected to the cylindrical portion of the outer tube being illustratedas a representative type of operator.

In the form of nozzle shown in Figures 5 and 6 the rearward taper of thenozzle 2 is relatively gradual and extends over a considerable distance.Consequently the external adjusting tube of the type described above andshown in Figures 1 to 4 is not well adapted to effect the adjustment ofthe orifice area in such a nozzle. In this instance, therefore, theorifice adjusting tube is received telescopically and concentricallywithin the end of the nozzle 2. Such tube is of rearwardly taperedfrusto-ccnical shape, preferably having the same cone angle as that ofthe main nozzle tube 2.

The tube 2!) is supported for adjustment lenthwise of nozzle 2 by a rod2f, carrying plates 22 which are disposed radially of the adjustabletube. Four such plates arranged mutually perpendicular are suificient tointerconnect the tube 20 and rod 2| securely. The sup-porting rod isreceived slidably in a block 23, which is protected from contact withthe hot reaction jet gases by a conical shield 24 located concentricallywithin the outer tube 2.

If the adjustable tube 29 is in its rearmost position its wall willengage the tip of the nozzle 2 and will extend unbrokenly incontinuation of the nozzle wall. As the rod 2| is slid forward anannular space is formed between the rearward end of nozzle 2 and thewall of tube 20. The farther the rod is pulled forward the greaterbecomes the space between the nozzle and the adjustable tube, and theeffective radial width of the annular jet space increasescorrespondingly. The aggregate jet area is thus progressively enlargedeven though the discharge aperture centrally of tube 20 remains constantin size. The adjustable tube may be moved forwardly sufilciently far tobring its rearward end into the same plane transversely of the nozzletube as the tip of the outer nozzle tube, thus establishing the maximumannular jet space. In such position the effective jet area will be thearea of the end of the outer or principal jet tube 2.

It will be appreciated that with either of my arrangements of compositetelescoping tube jet nozzles the size of the effective escape orificefor the gases may be varied between a minimum size, equal to the tiparea of the inner tube, and a maximum size, equal to the tip area of theouter tube, by lengthwise movement of the adjustable tube. As theeffective area of the composite jet aperture is increased the dischargevelocity of the gases will be decreased, (assuming acQIlSWRt volumetricflow) and consequently the thrust force produced will not be as great,but the efficiency of operation will be higher. On the contrary theeffective area of the composite orifice may be decreased, resulting in agreater velocity of the jet gases emitted from the nozzle and acorresponding thrust increase, although the efficiency of the jetoperation will not be as great.

The only difference in manipulation of the two types of adjustablenozzle described is that the efiective jet area is increased in theouter adjustable tube type by shifting the movable tube rearwardly,whereas in the inner adjustable tube type the movable tube must beshifted forwardly to increase the jet area. Consequently the impactforce of the jet gases against the adjustable tube tending to shift itrearward tends to increase the area of the jet orifice when the outertube is shiftable, whereas such force tends to reduce the jet orificearea in the shiftable inner tube type. In either structure the variationin jet area effected by a given movement of the adjustable tubelengthwise of the stationary tube can be decreased by reducing the coneangle of both tubes, and vice versa. Also the proportional variation inthe composite jet orifice will be affected by the size of the orificethrough the inner tube.

In either of the illustrated forms it will be evident that turbulence offlow is inappreciable, and that the relative velocities of gasesemerging from the inner and outer orifice portions remains substantiallyunaltered throughout a wide range of positional adjustment between innerand outer tubular members.

I claim as my invention:

1. In a jet motor for aircraft propulsion, a jet nozzle comprising aninner tube includin a forward'portion of constant exterior cross-sectional shape lengthwise thereof and a rearwardly tapered rearwardportion spaced lengthwise to define a circumferential aperturetherebetwee'm, an outer tube including a forward outer tube portion ofconstant interior cross-sectional shape lengthwise thereof, slidablyencircling the forward portion of said inner tube and a rearward outertube portion rearwardly tapered and adjoining said forward outer tubeportion and of a length greater than the length of the circum-'ferential aperture between the forward ancitapered rearward portions ofsaid inner tube, and means operable to shift one of said outer and innertubes relative to the other length-wise between a position in which thetapered rearward portion of said outer tube closes the circumferentialaperture between the forward and rearward portions of said inner tube,and a position in which the tapered rearward portion of said outer tubeis spaced outward from the tapered rearward portion of said inner tubeto define an orifice opening between the rearward end of said outer tubeand the outer surface of the tapered rearward portion of said innertube, which orifice opening communicates with such circumferentialaperture of said inner tube.

2. In a jet motor for aircraft propulsion, a jet nozzle comprising aninner tube including a cylindrical forward portion and a rearwardlytapered frusto-conical rearward portion spaced lengthwise to define anannular aperture therebetween, an outer tube including a cylindricalforward portion slidably encirclin the cylindrical forward portion ofsaid inner tube, and a rearward outer tube portion rearwardly taperedfrustomonically and'adjoining said forward outer tu e po on and of a lng h g eater than the annular aperture between the forward and taperedrearward portions of said inner tube, and means operable to shift saidouter tube lengthwise relative to said inner tube between a forwardposition in which the frusto-conicalrearward portion of said outer tubecloses the annular aperture between the forward and rearward portions ofsaid inner tube and the frusto-conical portions of said inner and outertubes are disposed in substantially unbroken continuation, and arearward position in which the frustoconical rearward portion of saidouter tube is spaced outward from the frusto-conical rearward portion ofsaid inner tube to define an annular orifice opening between therearward end of said outer tube and the outer surface of thefrustoconical rearward portion of said inner tube, which orifice openingcommunicates with such annular aperture of said inner tube.

3. An aircraft propulsion jet comprising an inner cylindrical shellcommunicating internally with the aircraft jet-motor combustion chamberand forming a substantially continuous duct tapered at its exhaust endto define an inner jet orifice at such end, the tapered end portion ofsaid inner shell having a discharge aperture therein by passing saidinner jet orifice, spaced from its exhaust end, and an outer cylindricalshell closely encircling said inner shell and having a rearward endportion tapered rearwardly to define an outer jet orifice ductencircling said inner orifice duct and communicating therewith throughsaid aperture.

4. An aircraft propulsion jet comprising an inner cylindrical shellcommunicatin internally with the aircraft jet-motor combustion chamberand forming a substantially continuous duct tapered at its exhaust endto define an inner jet orifice at such end, the tapered end portion ofsaid inner shell having a discharge aperture therein by-passing saidinner jet orifice, spaced from its exhaust end, an outer cylindricalshell closely encircling said inner shell and having a rearward endportion tapered rearwardly at substantially the same angle as said innershell to define an end-opening cuter jet orifice duct encircling saidinner orifice duct and communicating therewith through said aperture,means guiding said outer shell for adjustment endwise relative to saidinner shell to vary the radial width of said outer jet orifice duct, andthereby the outer orifice area, and adjustment means operativelyconnected with said outer shell and located wholly outside said outershell and out of the path of heated gases therein, and operable to shiftsaid outer shell endwise to vary the area of said outer orifice.

5. An aircraft propulsion jet comprising an inner cylindrical shellcommunicating internally with the aircraft jet-motor combustion chamberand forming a substantially continuous duct tapered at its exhaust endto define an inner jet orifice at such end, the tapered end portion ofsaid inner shell having an annular discharge aperture therein by-passingsaid inner jet orifice spaced from its exhaust end, an outer cylindricalshell telescoping slidably over the end portion of said inner shell andhaving a rearward end portion rearwardly tapered at substantially thesame angle as said inner shell to define an outer jet orifice ductencircling said inner orifice duct, communicating therewith through saidaperture, and adjustable in crosssectional area by telescoping movementof one shell efiected relative to the other, the inside dimension of therearward tip of the tapered end portion of the outer shell being lessthan the corresponding outer dimension of the inner shell at therearward edge of the aperture therein so as to close substantiallycompletely said aperture in the forward limit position of the outershell relative to the inner shell, and adjustment means disposed outsideof both shells and operatively connected with said outer shell to shiftsaid outer shell endwise from said limit position; to increaseprogressively the opening area of said outer orifice.

6. An aircraft propulsion jet comprising an inner substantiallycontinuous duct communicating with the aircraft's jet-motor combustionchamber and tapered rearwardly at its exhaust end to define an inner jetorifice, the ducts tapered wall portion having anexternally-communicating aperture therein, occupying a substantial wallarea and spaced forwardly of the rearward, or exhaust, end of such wallportion, an outer duct at least partly surrounding, and communicationwith, said inner duct through said aperture and paralleling the taperedwall portion of said inner duct to the exhaust end of said outer duct todefine an outer jet orifice adjacent to said inner orifice, and meansoperable, while maintaining said parallel relationship, to adjust thespacing between the outer ducts inner wall and the inner ducts outerwall to vary the outer ducts jet orifice opening and thereby theeffective opening of the composite jet formed by both ducts.

7. An aircraft propulsion jet comprising an inner substantiallycontinuous duct communicating with the aircrafts jet-motor combustionchamber and tapered rearwardly at its exhaust end to define an inner jetorifice, the ducts tapered wall portion having anexternally-communicating aperture therein, occupying a substantial wallarea and spaced forwardly of the rearward, or exhaust, end of such wallportion, an outer duct at least partly surrounding, and communicatingwith, said inner duct through said aperture and paralleling the taperedwall portion of said inner duct to the exhaust end of said outer duct todefine an outer jet orifice adjacent to said inner orifice, meansoperable, while maintaining said parallel relationship, to adjust thespacing between the outer ducts inner wall and the inner ducts outerwall to vary the outer ducts jet orifice opening and thereby theeffective opening of the composite jet formed by both ducts, and meansmounting said adjusting means wholly externally of both ducts.

8. An aircraft propulsion jet comprising an inner cylindrical shelldefining a substantially continuous duct communicating with theaircrafts jet-motor combustion chamber and tapering at its exhaust endto define an inner jet orifice, said shell being articulated in itstapered end portion to define a substantially full annular aperturewhose rearward annular boundary is of substantially lesser diameter thanits forward annular boundary because of the taper, effectively toprovide a direct by-pass path for gases passing through said duct towardsaid inner jet orifice, an adjustable outer shell encircling the taperend of said inner shell, comformably tapered and overlying said apertureto define an annular outer by-pass duct and jet orifice adapted todischarge gases into a stream converging with the inner orifice expelledstream, and adjustment means operable to shift said outer shell axiallybetween a forward position blocking flow through said aperture andsubstantially closing said'outer jet orifice, and a rearward positiondefining a relatively large outer jet orifice, the structure thusdefined providing a velocity relationship between the inner and outerjet substantially uncharged throughout adjustment of. the outershell.

9. 'An aircraft propulsion jet comprising an inner cylindrical shelldefining a substantially continuous inner duct communicating with theaircraft's jet-motor combustion chamber and tapering at its rearward orexhaust end to define an inner jet orifice, a tapered outer shell ofsubstantially equal taperangle, surrounding said inner shell and movableaxially thereof to define, between said shells, an annular duct of anadjustable width which is substantially constant over the overlappingtapered lengths of the shells, the rearward end of .said outer shelldefining an outer jet orifice and being larger than the correspondingend of the innershell, an annular aperture located in the taperedportion of said inner shell and underlying said outer shell, therebycommunicating with said outer duct, and means operable to adjust theposition of said outer shell axially relative to said inner shell tovary the width of said outer duct between said aperture and outer jetorifice, thereby to preserve substantially the same relative jetvelocities through said outer orifice and adjacent inner orifice.

ROBERT PLATH.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 576,259 Diamond Feb. 2, 1897658,586 Reiling Sept. 25, 1900 20 1,319,782 Maul Oct. 28, 1919 1,536,630Reinecke May 5, 1925 2,408,099 Sherman Sept. 24, 1946

